To kill weeds or harmful insects, or to prevent diseases, agricultural chemicals are sprayed on agricultural plants. If the sprayed agricultural chemicals remain uneven on the plants unevenly, high efficacy may not be expected. To evenly spread the agricultural chemicals on the plants in a period of time as short as possible and to promote penetration of the active ingredient into the plant leaves before washed away by rain, an agricultural spreading agent comprising a surfactant has been used. Examples of such surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene higher fatty acid ester. Silicone surfactants have also been used on account of their low toxicity and high surface activity.
Japanese Patent Publication No. 6-55642 discloses a polyether-modified silicone having a trisiloxane backbone. The silicone has a high surface activity and is put to a practical use as a spreading agent for agricultural chemicals.
The aforesaid silicone has a drawback that the surface activity thereof decreases in an acidic or an alkaline pH. As a silicone to overcome the drawback, Japanese Patent Application Laid-Open No. 2000-327787 discloses a silicone having a modified trisiloxane backbone.
Meanwhile, it is known from J. Agric. Food Chem., 34(2), 235 that a spray agent on the basis of hydrocarbon oil or plant extract oil have an insecticidal effect by blocking spiracle openings of harmful insects and enhancing penetration of agricultural chemicals into leaves of agricultural plants. However, the hydrocarbon oils and, particularly, plant extract oils have high surface tension and, therefore, do not wet leaves well.
EP 0648413A1 describes a method for reducing the surface tension of the oils by adding an alkyl-modified silicone. R. E. Gaskin et al. describe in “SPRAY OILS-BEYOND 2000”, University of Western Sydney, that spreadability and accordingly a pesticidal effect of plant extract oils are significantly improved by using an alkylsilicone.
W001/087063 describes that polyhydric silicones having a group having at least three hydroxyl groups and silicones having two hydroxyl groups and a polyoxyethylene moiety are surface active. As the group having hydroxyl groups, sugars are referred to.
However, the aforesaid silicones of the prior art need further improvement in their surface activity.